1. FIELD OF THE INVENTION
The present invention concerns the salient poles of synchronous electrical machines and, more particularly, of synchronous machines intended for starting up contingently as synchronous motors and comprising, for that purpose, a damping system constituted by a surface of zone of the pole shoe.
2. Description of the Prior Art
That surface zone of each pole is the seat of a flow of Focault currents during the asynchronous operation of the machine; interpolar connections enable the passing of those currents from one pole to the other.
That surface zone undergoes heating which increases as the energy to be brought into play to bring the rotor into synchronism is increased and as the starting up time is reduced. In the case where the poles are completely solid, the heating affects only a small surface thickness of each pole, the remainder of the polar body keeping its original temperature. Great thermal stresses which limit the use of this type of pole result from this.
The present invention is intended to reduce greatly these thermal stresses by giving the polar body sufficient deformability to enable it to follow more freely the expansions of the heated surface zone.